Liquid dispensing systems are commonly used for numerous purposes, the most prevalent of which involves vending machine or soft drink dispensing applications. Normally, the liquid dispensing system includes a plurality of bag-in-box storage containers, wherein a liquid such as flavored syrup, commonly one of a number of flavors, is stored for later use within a rigid box. The syrup is normally stored in a flexible bag located within the rigid box; the bag adapted to collapse as the syrup is used. These types of storage containers have been found to be particularly useful for soft drink dispensing applications, because of the ease of storing the rigid boxes and the ease with which the flexible bags can be refilled for additional use. It is known that in the process of filling the bag contained within the rigid box a volume of unwanted air, or another gas, is often introduced into the bag and is inadvertently stored in the bag along with the syrup.
Normally, when the bag-in-box storage container is attached to the remaining components of the liquid dispensing system, the unwanted air contained in the bag will be introduced into a supply line and eventually caused to pass through a pump into a dispensing tower. This unwanted air in the syrup supply line creates numerous problems. The foremost of these problems is that air in the syrup supply line will meet with carbonated water, which is introduced into the liquid dispensing tower from a carbonated water supply line, and the rapid decrease in partial pressure of the carbon dioxide in the carbonated water will cause excessive foaming of the dispensed soft drink. This excessive foaming is highly undesirable and results in numerous problems. In addition, air in the syrup supply line will also cause intermittant operation, more commonly known as "burping", with the attendant splashing of the dispensing liquid.
Excessive foaming of the dispensed soft drink requires that the operator of the liquid dispensing system terminate the filling cycle substantially before the soft drink container is completely filled. This requires that the operator re-initiate the filling cycle, possibly a number of times, to "top off" the drink. In addition, excessive foaming also causes expensive spillage of the dispensed soft drink, which causes unnecessary waste problems and creates a generally unsanitary condition of the work station with possible appearance problems.
Recognizing the undesirable results occassioned by the presence of unwanted air introduced in the syrup supply line, the industry has responded to this problem by placing a reservoir along the length of the syrup supply line and providing a bleed valve in the reservoir, whereby a certain amount of syrup is introduced into the reservoir and accumulates in the bottom of the reservoir with the result being that any air existing in the syrup supply line prior to the reservoir is collected in the upper portion of the reservoir and then removed from the reservoir by selective operation of the bleed valve.
Although these types of systems have been shown to be successful in certain applications, these particular types of systems have additional disadvantages. For example, the bleed valve may require operator attendance or a back-up system to relieve the air that has accumulated within the reservoir.
In another commercial device, a reservoir is positioned along the high pressure side of the syrup supply line, i.e. after the pump. The reservoir has an inlet and an outlet and includes a float. The float operates to automatically open a bleed valve as it falls in the reservoir; the result being that any excess air accumulated in the reservoir is evacuated. The primary disadvantage of this system was that the reservoir was on the high pressure side of the pump, which caused possible spillage if the float failed to operate. This reservoir construction was also ineffective at removing substantially all small bubbles located in the syrup.
In addition, for high-speed dispensing applications, wherein the soft drink is being dispensed at flow rates far in excess of those previously achievable, it has been found that the use of a reservoir and bleed valve system is insufficient to prevent air from being drawn into the syrup supply line after the reservoir and pumped with the syrup to the dispensing tower.
Thus, it is desirable that an automatic air evacuation apparatus be employed to collect air that is contained in the syrup supply line extending from the bag-in-box supply system and automatically evacuate that air, so as to prevent its passage into and through the primary syrup pump and eventually to the dispensing tower.